A phase shift full-bridge zero-volt switching (ZVS) operation has been proposed as an effective scheme for supporting mutual compatibility between enhancement of efficiency of a switching power device and noise reduction, compared with the related arts.
In the switching power device of the related art, a simultaneous OFF time (also known as a dead time) of an upper switch and a lower switch is set to be long in order not to interrupt the soft switching operation (ZVS operation) even when a load is light or a device delay is great.
However, when the long simultaneous OFF time is fixedly set, a high enough efficiency may not be achieved when a load is heavy or a device delay is small.
In addition, an optimal value of the simultaneous OFF time for achieving the highest efficiency is significantly changed by manufacturing deviations of upper and lower switches, transformers, or the like, and is also significantly changed by the magnitude of current flowing in such components.